The followup question is a little more complex - "Why exactly is Mr Wombat in there today after being in there until half past one in the morning last night?"
And now the funny story.
Yesterday evening at around six or seven, after everyone had gone home (including myself to get some dinner before coming back in) our HR/Accountant/Admin person was walking back to her office when she noticed a strange man hanging out of the bars on the window of the hall outside her office. This window is pretty inaccessible being as how it's on the first floor over a sunken courtyard. The place has been burgled once or twice and more than a few attempts have been made recently too, so she made the natural assumption that the man hanging from the bars over the window, a good ten feet up in the air, was up to no good.
She turned to him and asked "What the hell do you think you're doing?" to which he replied "Well, I'm not the fucking window cleaner now am I?" then dropped to the ground and legged it.